9:10 p.m. — Flash flood warning from McLean through northwest Washington to Beltsville until midnight
While storms were slow to develop this evening, they have increased dramatically in coverage and intensity especially in areas north of downtown Washington. Heavy storm cells, passing over the same areas repeatedly, has prompted a flash flood warning from northeast Fairfax County through northwest Washington into southern Montgomery County until midnight.
“Between 2 and 3 inches of rain have fallen,” the National Weather Service writes. “Additional rainfall amounts of 1 to 2 inches are possible in the warned area. Flash flooding is ongoing or expected to begin shortly.”
Best to avoid traveling in this zone until this rain subsides. Remember to never attempt to drive across a flooded road. Turn around, don’t drown.
Based on radar trends, conditions should improve between 10 and 11 p.m. in this flash flood warning zone.
Aside from this complex of heavy storms triggering the flood warning, just one other storm caused issues earlier this evening. Between 7 and 8 p.m., a severe storm passing between Potomac and Rockville unleashed strong winds which brought down trees, including one on a home:
(~715p) 11800 Coldstream Dr. off Tuckerman La, Potomac, large tree struck occupied home, no injuries however four (4) people & two (2) dogs will be displaced, Power out in area pic.twitter.com/pnHCtlGUgI
Both severe thunderstorm and flood watches are in effect in a region stretching from Virginia to New Jersey through this evening due to the likelihood of storms, especially between about 5 and 10 p.m. The main three hazards with any storms will be torrential rain, lightning and some damaging wind gusts.
Remember that a severe thunderstorm watch means ingredients are in place for intense storms but may or may not come together. However, if a severe thunderstorm warning is issued for your location, it means an intense storm is imminent and you should seek shelter.
A severe thunderstorm watch has been issued for parts of Delaware, District of Columbia, Maryland, New Jersey, Pennsylvania and Virginia until 9 PM EDT pic.twitter.com/ssV8JYzFwS
As of late this afternoon, a few storms have already popped up along the Interstate 64 and Interstate 81 corridors, but there are no imminent storms in the immediate metro region. Strong to severe storms are most probable during the evening hours — especially toward sunset.
Calmer weather will move in Sunday, with rain chances diminishing quickly in the morning, and then clearing skies during the afternoon.
Through tonight: Thunderstorms may slowly close in on the region through the evening hours. The main threats are damaging wind gusts in some storms. Secondarily, we have the threat of flooding downpours and lighting. At least a half inch of rain is possible for many of us, but a quick one or two inches of rain inside the heaviest of thunderstorms can’t be ruled out.
Additional showers or lesser thunderstorms are possible later into the night as temperatures bottom out in the upper 60s and low 70s. We’ll monitor the rain amounts late night to make sure they don’t exacerbate flooding issues from earlier storms.
Tomorrow (Sunday): Final showers will move out of the region in the morning, as light southwest breezes turn toward the northwest, indicating that the cold front has passed. Southern Maryland may be the last place in the region to clear its showers, perhaps midday.
After showers end, we all have a couple more hours of clouds behind them but afternoon skies will be bluer. High temperatures may range from 83 to 88 degrees, and humidity levels will slowly head downward.
Tonight the area around the Beltway should most keep an eye on the 6 to 9 p.m. window. That is when storms may most target the D.C. area and Interstate 95 corridor. A few storms could linger after that, but the potential for damaging wind gusts should diminish a bit before the flooding downpour threat.
Small hail and frequent lightning are also a possibility this evening, even after the strongest of storms die down somewhat after 9 or 10 p.m. Always keep in mind “when thunder roars, head indoors” — if you hear thunder, lightning is close enough to strike.
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